The invention relates to machines for paving roads. In particular, the invention pertains to self-propelled paving machines capable of picking-up a windrow of loose paving material without the assistance of additional equipment.
In the past, pavers were independent machines which evenly distributed loose paving material from a holding bin or hopper in the paver to the road directly in front of a screed supported on the paver to produce a road surface from loose paving material. The loose material was previously dumped into the hopper or holding area of the paver by use of a dump truck or other separate apparatus. More recently, Astec Industries developed a "shuttle buggie" device, which is the subject of U.S. patent application Ser. No. 89,318. The shuttle buggie transports paving material from a dump truck or a windrow to the paver and then discharges the paving material into the paver by way of a conveyor.
Employing a single machine to pick up loose paving material laid in a windrow and pave the surface over which the machine passes avoids the need for separate windrow pick-up or "shuttle buggie" machines. Prior attempts have been made to develop such a combined pick-up and paving device, such as that shown in the Babler U.S. Pat. No. 4,200,408 (a similar device also was built by CMI Corporation).
The '408 patent shows a pavement laying apparatus equipped with an upwardly inclined chute hinged on a hopper front wall and a conveyor supported on the front of the paver. This type of device suffers from several problems. First, any loose paving material which gets beyond the chute will travel beneath the wheels of the paver causing the paver to rise above the road surface. As the paver rises above the road surface, the chute will be carried to a higher level above the road surface and allow yet more paving material from the windrow to travel under the paver and raise the paver even further. This process will continue until a significant portion of the windrow is not picked up by the chute and the paving function of the machine is seriously disrupted.
A second problem with the Babler-type of paver is that it cannot adjust to the road grade relative to the rest of the paver, i.e. it is fixedly attached to the paver about that axis. Additional problems include the fact that on the Babler-type paver, the chute and flight conveyors contained in the chute must be as wide as the windrow or, if not, guide plates are used to funnel the windrow into the chute. Often these guide plates allow a significant amount of paving material underneath the chute or are lifted above the ground when the paver rolls over loose material which passes under the conveyor.
Another problem apparent in the Babler device is the danger of the chute violently colliding with a hidden obstruction. For example, the Babler paver would violently collide with a manhole cover buried under a windrow of paving material causing damage to the chute or other parts of the paver and, possibly, injury to the operator.
It is an object of the present invention to provide an improved integrated paver having windrow pick-up capability.
It is another object of the present invention to provide a paver having front apparatus for picking-up a windrow of paving material and depositing it into the paver, the front apparatus having the ability to pivot to adjust for both tilt and grade adjustments relative to the rest of the paver.
It is yet another object of the present invention to provide a paver which can at least semi-automatically adjust the tilt of the conveyor relative to the paver in order to avoid a gradual lifting of the paver off the road surface because of leakage of paving material past the conveyor.
It is further an object of the present invention to provide a conveyor which will not violently collide with manhole covers or other obstructions hidden in the windrow.
It is yet another object of the present invention to provide a way of feeding a windrow which is wider than the conveyor into the conveyor without the attendant problem of using funneling guides.
It is yet a further object of the present invention to provide a conveyor which will have reduced vibrations and be more efficient in conveying the loose paving material in the windrow into the paver hopper.
Other and further objects will become apparent from the following discussion of the invention and its embodiments.